Method of fabricating a photoconductive pickup tube

ABSTRACT

A method of fabricating a photoconductive pickup tube utilizing a one-piece envelope, with a closed-end faceplate portion, wherein a unitized mount structure is positioned. The integrated mount includes a beam forming portion with a mesh electrode oriented relative to the frontal end thereof. The unitized array continues whereof a target substrate, having a photoconductive target electrode formed thereon, is insulatively spaced from the mesh electrode. Resilient means are terminally employed to spaced the target substrate from the interior surface of the envelope faceplate, and a connective means for the target electrode is extended in an insulated manner along the mount to emerge from the base portion of the envelope.

limited States Patent Miller et a1.

[54] METHOD OF FABRICATING A PHOTOCONDUCTIVE PICKUP TUBE [72] Inventors: John J. Miller, Seneca Falls; Carl W. Penird, Waterloo, both of NY.

[73] Assignee: Sylvania Electric Products Inc.

[22] Filed: May 24, 1971 [21] Appl. No.: 146,301

Related US. Application Data [62] Division of Ser. No. 11,616, Feb. 16, 1970, Pat.

[52] US. Cl ..3l6/l9, 29/2513 [51] Int. Cl ..H0lj 9/18 [58] Field of Search ..3l6/18, 19, 24; 113/65 A;

[56] References Cited UNITED STATES PATENTS Antoniades ..3 13/65 A Shallcross ..313/65 A [15] 3,692,379 51 Sept. 19, 1972 3,256,455 6/1966 Saloi ..3l3/65 A 3,376,446 4/1968 l-laan et al ..3l3/65 A Primary Examiner-John F. Campbell Assistant Examiner-D. M. Heist AttorneyDonald R. Castle and Frederick H. Rinn [57] ABSTRACT A method of fabricating a photoconductive pickup tube utilizing a one-piece envelope, with a closed-end faceplate portion, wherein a unitized mount structure is positioned. The integrated mount includes a beam forming portion with a mesh electrode oriented relative to the frontal end thereof. The unitized array continues whereof a target substrate, having a photoconductive target electrode formed thereon, is insulatively spaced from the mesh electrode. Resilient means are terminally employed to spaced the target substrate from the interior surface of the envelope faceplate, and a connective means for the target electrode is extended in an insulated manner along the mount to emerge from the base portion of the envelope.

4 Claims, 5 Drawing Figures PATENTEBsEP 19 1922 I v 3,692. 379

SHEETlUFZ ll 4 6 57 2 15 5 45 l9 INVENTOR J HN J.' MILLER 8.

CARL W. PEN/RD ATTURNEY P ATENTED 19 I973 3,692,379

sum 2 UF 2 JOHN I MILLER 8 CARL w. PENIRD ATTORNEY INVENTORS.

METHOD OF FABRICATING A PHOTOCONDUCTIVE PICKUP TUBE CROSS REFERENCE TO RELATED APPLICATION This application is a divisional application of Ser. No. 011,616, filed Feb. 16, 1970, now US. Pat. No.

3,619,685, which is assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION This invention relates to cathode ray tubes and more particularly to a method of fabricating a photoconductive pickup tube of the type utilized in television camera applications.

Many of the photoconductive tubes conventionally utilized in television applications are normally relatively complicated structures, and as such are not readily conducive to expeditious methods of fabrication. It was found extremely difficult to consistently form photoconductive target electrodes on the face areas of closed end tubes and make satisfactory electrical connections thereto. In view of this difficulty, it has been common practice to construct pickup tubes having the photoconductive target electrode disposed on the inner surface of a separate glass faceplate which is then usually indium-sealed to an open envelope portion. It has been conventional practice to utilize the indium seal as a means for effecting an external connection for the target electrode. Such seals were found to be expensive, first, in view of the cost of the indium material seal, and second, because of the special treatment that must be given the glass to insure hermetic tightness.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide a method fabricating a photoconductive pickup tube of a structure that can be expeditiously and inexpensively executed.

Another object is to provide a method of fabricating a pickup tube wherein the target electrode is not directly associated with the faceplate of the tube.

A further object is to provide a method of fabricating a pickup tube by considering the internal tube structure as a wholely separate construction.

The foregoing objects are achieved in one aspect of the invention by providing a method of fabricating a pickup tube employing a one-piece envelope having a closed-end faceplate wherein a stacked array of related elements is positioned as a unitized mount structure. The integrated array in the unitized mount includes a basic multi-electrode beam forming structure, upon which a mesh electrode is oriented relative to the frontal open end thereof. Spaced from the mesh electrode, by insulative spacer means, is a transparent target substrate having a photoconductive target electrode formed on the rear surface facing the mesh electrode. Relative to the front surface of the target substrate are terminal spacing means peripherally and longitudinally oriented to provide resilient spacing between the target substrate and the interior surface of the envelope faceplate. Target electrode connective means are extended longitudinally in an insulated manner along the mount structure to emerge from base portion of the envelope. The aforedescribed photoconductive pickup tube utilizing the unitized mount construction and onepiece envelope concepts can be expeditiously and economically fabricated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section view showing a photoconductive tube incorporting the concepts of the invention;

. FIG. 2 is an enlarged cross-section of the forward portion of the tube detailing aspects of the invention as viewed relative to the line 2-2 of FIG. 3;

FIG. 3 is a plan view showing the end of the mount structure taken along the line 3-of FIG. 2;

FIG. 4 is an enlarged cross-section of the forward portion of the tube illustrating another embodiment of the invention; and

FIG. 5 is a perspective illustrating an alternate embodiment of the terminal spacing means.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

The term one-piece envelope as used herein is intended to include a bulb structure wherein the closed end or faceplate portion is:

l. a continuation of the same glass comprising the envelope sidewall; or

2. of different glass than that of the envelope sidewall but expansively compatible therewith.

With reference to the drawings, there is shown in FIG. 1 a photoconductive pickup tube 11 having a onepiece evacuated envelop 13 which comprises a wall portion 15, an integral closed-end faceplate portion 17, and an opposed base closure portion 19. Positioned therein in a unitized internal mount construction 21 which is supported by the base portion 19 and comprises a multielectrode electron beam forming structure of which only a substantially tubular control electrode 23 is shown. A plurality of electrical connective means 22 are arranged to extend exteriorly from the internal mount structure 21 through the base portion 19. A substantially planar mesh electrode 25 is supported relative to and parallel with the open frontal end of the control electrode 23. Spaced from the mesh electrode 25, by spacer means 27, is a substantially transparent planar target substrate 29 which is supported by an annular support means 33. A photoconductive signal or target electrode 41 is suitable formed on the rear surface of the substrate 29 facing the mesh electrode 25. An electrical connection 45 for the target electrode 41 is formed and disposed to extend longitudinally in an insulated manner along the mount structure 21, in the space between the control electrode 23 and the envelope wall portion 15, to emerge from the base portion 19 as an external connection 45'. Extending longitudinally beyond the target substrate 29 are terminal spacing means 49 which are disposed in a peripheral manner to provide substantially resilient spacing between the target substrate and the interior surface of the envelope faceplate 17. A longitudinal axis 55 extends through the one-piece envelope 13 and the encompassed internal unitized mount structure 21. At least three resilient spaced apart positioners 56 are employed to effect lateral support and positioning of the mount structure 21 within the envelope 13.

In operation, light rays 57 from external imagery are focused on the photoconductive target electrode 41 by camera lens means 59. In the pickup tube 11 of this invention, the light rays 57, that have passed through the lines 59, are directed to traverse the tube faceplate portion 17 in an Lin-focused condition. As such, the optical quality of the glass comprising at least the central portion 17' of the faceplate 17 should be substantially free of optical distortion but need not be as critical as the quality of the glass of the target substrate 29 which is contiguous to the plane of focus on the target electrode 41. Utilization of the foregoing optical considerations plus the orientation of the target electrode connection through the base portion makes the one-piece envelope concept a feasible and advantageous construction.

With reference to FIGS. 1, 2, and 3, the structure and fabrication of one embodiment of the pickup tube 1 l of the invention will be described in greater detail.

The substantially transparent planar target substrate 29 is of distortion free glass, such as one of the clear borosilicates, having smooth front and rear surfaces, 30 and 31 respectively. On the rear surface 31, a substantially uniform and transparent electrically conductive coating 32 is formed in a conventional manner, such as by heating the substrate and spraying substantially the whole of the rear surface 31 with stannic chloride to form conductive tin oxide. The conductively coated substrate 29 is then positioned in the female section of the substrate annular support means 33 in a manner that the electrically conductive coating 32 makes contact with an instanding ledge or shelf 37 of the female support section 35. With the substrate 29 so positioned, a photoconductive material 39, such as for example antimony tri-sulphide, is suitably vaporized over the exposed coating of tin oxide 32 to form the target electrode 41. A metallic male section 42 of the annular support means 33, having resilient terminal spacing means 49 positioned and attached thereto, is then inserted into the female support section 35 to substantially peripherally seat upon the uncoated front surface 30 of the substrate. The male section 42 has a peripheral wall 43 which makes engagement with the peripheral wall 36 of the female section 35. The two sections 35 and 42 of the annular support means 33 are then bonded together such as by welding the peripheral wall 36 to the wall 43 to form an electrically conductive and supported target electrode structure 47.

The mesh electrode 25 is a planar foraminous screen which, depending upon the resolution desired in the tube, may have from 500 to 1,000 apertures per inch. This mesh screen is supported by a flanged support ring 26 which, as shown in FIG. 2, is positioned on and bonded to the open frontal end of the control electrode can be of the electron beam forming structure.

Target spacer means 27, in the form of an insulative ring circumferentially dimensioned to have an opening at least substantially equalling the functional area of the mesh electrode 25, is peripherally positioned between the mesh electrode 25 and the target or signal electrode structure 47 to provide a stacked array of cooperating elements. It has been found that the target spacer 27 can suitably formed from ceramic or glass. A target electrode connective lead 45 is terminally formed to facilitate bonding attachment to the target electrode structure 47 in a manner to function as both an electrical connection and support means therefor. The connective lead 45 extends along the control electrode 23 encased in an insulator or standofi 24 which is attached to the mount structure by clamping means 65. At least one target electrode structure support 61, spaced from the connective lead 45, is also bonded to the target electrode structure 47. As shown in FIGS. 2 and 3, three of such structure supports 61 are insulatively attached to the exterior wall of the control electrode 23 by insulators 63 and welded clamping means 65. Thus, by the bonded electrode connective lead 45 and one or more of the structure supports 61, a stacked unitized mount structure 21 is provided.

Reference is again made to the terminal spacing means 49. As shown in FIGS. 2 and 3,.three substantially S-shaped resilient metallic elements or snubbers, referenced as 49, are spacedly positioned and bonded to an instanding ledge or shelf 51 of the male support section 42. These snubbers 49 are formed to extend beyond the target electrode structure 47 in a manner to contact the periphery of the envelope faceplate portion 17. The S-shaped resilient elements are not to be considered limiting as other configurations can function in a similar manner. For example, a metallic wigglewasher 49', as shown in FIG. 5, is vertically formed to seat on the instanding ledge 51 and provide the required terminal resilient spacing. This washer 49' may or may not be bonded to the ledge 51 and is circumferentially dimensioned to have an opening at least substantially equalling the functional area of the target photoconductive material 39.

Another embodiment of the forward end of the unitized mount structure 21 is shown in FIG. 4 wherein the mesh electrode 25' is electrically isolated from both the control electrode 23 and the target electrode 41. In certain types of pickup tubes such isolation is desired. This is accomplished by positioning the mesh electrode 25 between the aforedescribed annular target spacer means 27 and a control electrode annular insulative spacer 71 which is formed in a manner similar to target spacer means 27 and seated on the open end of the beam control electrode 23. The insulated mesh electrode 25 may have a separate electrical connection 73 attached thereto and formed to extend longitudinally, encased in an insulator 75 attached to the control electrode 23, within the envelope in a manner to emerge outwardly through the base portion 19.

As in the first embodiment, the second embodiment is likewise supported and unitized by the target electrode connective lead 45' and at least two target electrode structure supports 61.

Upon being unitized, either mount structure is the inserted within the one-piece glass envelope in a manner that the resilient terminal spacing means 49, 49 makes seated peripheral engagement with the inner surface of the closed-end faceplate portion 17. It has been found that a clear soft lime glass is satisfactory material for the one-piece envelope construction.

While the terminal spacing means 49 of the unitized amount structure 21 are maintained in resilient engagement with the faceplate portion 17, base closure portion 19 is joined to the envelope 13 as by a conventional droptseal technique to provide a glass enclosed structure. Subsequent gas evacuation, hermetic sealing, and tube processing of the glass enclosed structure provides the completed photoconductive pickup tube 1 1.

It is within the scope of the invention to rearrange certain of the fabrication steps as may be deemed conducive to efficient manufacturing procedure.

Thus, a pickup tube structure is provided than can be expeditiously and inexpensively fabricated. By utilizing unitized mount construction, separate faceplate seals are eliminated, all electrical connections are feasibly effected through the base. By removing the target electrode from the faceplate, the optical quality of the faceplate is less critical to the application. Therefore, less expensive envelopes are employed, and the number of fabrication steps are reduced.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

We claim: 1. A method of fabricating a photoconductive pickup tube having an axis and formed of a one-piece glass envelope having a wall with a closed-end faceplate portion wherein there is substantially axially positioned an internal tube construction including a multi-electrode beam forming structure, supported on a base closure portion and having a mesh electrode oriented relative to the frontal open end thereof, an adjacently positioned transparent target substrate having a photoconductive target disposed on one surface, insulative target spacer means between the mesh electrode and the target substrate, annular support means for positioning the target substrate relative to the control electrode, terminal spacing means between the target substrate and the envelope faceplate, and longitudinally oriented internal connective means for the target electrode, said method comprising the steps of:

applying a coating of a substantially transparent electrically conductive material over substantially the whole of the rear surface of said target substrate;

positioning said coated substrate on a metallic female section of said annular support means in a manner that said conductive coating makes contact with a ledge instanding from the peripheral wall thereof;

applying photoconductive material over the electrically conductive coating on said substrate to form a target electrode;

positioning and attaching resilient terminal spacing means to a metallic male section of said annular support means;

inserting said male section of said annular support means into said female section to substantially peripherally seat upon the front surface of said substrate, the peripheral wall of said male section making engagement with the peripheral wall of said female section;

bonding said male and female sections of said substrate support means to form a supported target electrode s ctur positioning sal mes electrode relative to the open frontal end of a pre-formed multi-electrode beam forming structure;

positioning said target spacer means between said mesh electrode and said target electrode structure to provide a stacked array; insulatively attaching to said beam forming structure a target electrode connective lead and at least one target electrode structure support in a manner to provide a stacked unitized mount structure;

inserting said unitized mount structure into said glass envelope in a manner that said resilient terminal spacing means make seated peripheral engagement with the inner surface of said closed end faceplate portion; sealing said glass envelope to said base closure portion to provide a glass enclosed structure; and

evacuating, hennetically sealing and processing said glass enclosed structure to provide said photoconductive pickup tube contained within a one-piece envelope.

2. A method of fabricating a photoconductive pickup tube according to claim 1 wherein the positioning of said mesh electrode is accomplished by seating the supported mesh upon and electrically attaching it to the open end of said beam forming structure.

3. A method of fabricating a photoconductive pickup tube according to claim 1 wherein the positioning of said mesh electrode is accomplished in an electrically isolated manner by seating it on a control electrode annular insulative spacer oriented on the open end of said beam control electrode.

4. A method of fabricating a photoconductive pickup tube according to claim 3 wherein an electrical connection is provided for said mesh electrode, said connection being extended longitudinally along said mount within said envelope to emerge outwardly through said base closure portion.

PO-lOSO (5/69) 7 UNITED STATES PATENT OFFICE QERTMQATE or EQHN Patent No. 3,692,379 Dated September 19, 1972 John J. Miller and Carl W. Penird Inventor(s) It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 3 Line 60, delete "can be" and substitute therefor Column 4, Line 1, After "can" insert be 1 Signed and sealed this 10th day of April 1973 (SEAL) Attest:

EDWARD M.PLETCHER,JR. Attesting OPficer ROBERT GOTTSCHALK Commissioner of Patents 

1. A method of fabricating a photoconductive pickup tube having an axis and formed of a one-piece glass envelope having a wall with a closed-end faceplate portion wherein there is substantially axially positionEd an internal tube construction including a multi-electrode beam forming structure, supported on a base closure portion and having a mesh electrode oriented relative to the frontal open end thereof, an adjacently positioned transparent target substrate having a photoconductive target disposed on one surface, insulative target spacer means between the mesh electrode and the target substrate, annular support means for positioning the target substrate relative to the control electrode, terminal spacing means between the target substrate and the envelope faceplate, and longitudinally oriented internal connective means for the target electrode, said method comprising the steps of: applying a coating of a substantially transparent electrically conductive material over substantially the whole of the rear surface of said target substrate; positioning said coated substrate on a metallic female section of said annular support means in a manner that said conductive coating makes contact with a ledge instanding from the peripheral wall thereof; applying photoconductive material over the electrically conductive coating on said substrate to form a target electrode; positioning and attaching resilient terminal spacing means to a metallic male section of said annular support means; inserting said male section of said annular support means into said female section to substantially peripherally seat upon the front surface of said substrate, the peripheral wall of said male section making engagement with the peripheral wall of said female section; bonding said male and female sections of said substrate support means to form a supported target electrode structure; positioning said mesh electrode relative to the open frontal end of a pre-formed multi-electrode beam forming structure; positioning said target spacer means between said mesh electrode and said target electrode structure to provide a stacked array; insulatively attaching to said beam forming structure a target electrode connective lead and at least one target electrode structure support in a manner to provide a stacked unitized mount structure; inserting said unitized mount structure into said glass envelope in a manner that said resilient terminal spacing means make seated peripheral engagement with the inner surface of said closed end faceplate portion; sealing said glass envelope to said base closure portion to provide a glass enclosed structure; and evacuating, hermetically sealing and processing said glass enclosed structure to provide said photoconductive pickup tube contained within a one-piece envelope.
 2. A method of fabricating a photoconductive pickup tube according to claim 1 wherein the positioning of said mesh electrode is accomplished by seating the supported mesh upon and electrically attaching it to the open end of said beam forming structure.
 3. A method of fabricating a photoconductive pickup tube according to claim 1 wherein the positioning of said mesh electrode is accomplished in an electrically isolated manner by seating it on a control electrode annular insulative spacer oriented on the open end of said beam control electrode.
 4. A method of fabricating a photoconductive pickup tube according to claim 3 wherein an electrical connection is provided for said mesh electrode, said connection being extended longitudinally along said mount within said envelope to emerge outwardly through said base closure portion. 